The present invention relates generally to locomotive diesel engines, and more particularly to a test assembly for generating a once-per-cycle signal for such engines phased to when a predetermined piston is at the top dead center of its cylinder.
Locomotive engines typically are two-stroke or four-stroke diesel engines having 8, 12, or 16 cylinders. Such engines also include conventional crankcases containing crankshafts for reciprocal motion of the pistons and camshafts for reciprocal motion of the valves. In the four-stroke engine, the crankshaft makes two revolutions per cycle, and the camshaft makes one revolution per cycle. A locomotive diesel engine condition monitoring and diagnostic system has been proposed for gathering in-service engine data to be used as a baseline for later periodic engine tests to determine if the engine is later experiencing actual or incipient problems. The goal of such proposed testing is to improve engine reliability and locomotive availability by replacing during routine inspections worn or damaged parts that are about to fail instead of replacing those parts after they have failed in service. Such in-service failures result in costly out-of-service time for the locomotives. Such proposed periodic testing of the locomotive diesel engines would be carried out when the locomotives are brought to railroad maintenance shops for routine engine inspection.
Such proposed engine diagnostic testing requires relating engine test data (such as engine vibration) to a once-per-cycle signal phased to when a predetermined piston is at the top dead center of a cylinder of the engine. Existing lab engines (stationary locomotive diesel engines bolted to the floor) and existing engineering engines (engines of engineering locomotives which run on tracks and are used for engineering research, test, and development) include exposed crankshafts having a special bearing and (for some such engines) an optically encoded disk attached thereto. A light aimed at the disk is used to generate a signal once per revolution of the disk. To install and remove such a test assembly as part of an engine diagnostic testing program on an in-service locomotive would require between four and six hours, a time not considered acceptable. What is needed is such a test assembly which can be installed and removed in a much shorter time.